U.S. patent application number 10/344301 was filed with the patent office on 2004-02-05 for method and system for measuring active animal glue concentration in industrial electrolytes.
Invention is credited to Bas, Wlodzimierz, Fuglewicz, Boguslaw, Garbaczewski, Jan, Gladysz, Olympia, Jagiello, Jan, Los, Przemyalaw, Malachowicz, Grzegorz, Nosal, Stanislaw, Orzecki, Stanislaw, Plinska, Gtanislawa, Przysiezny, MIroslaw, Romanowicz, Piotr, Szwancyber, Grzegorz, Urbanowicz, Roman, Warmuz, Marian.
Application Number | 20040020772 10/344301 |
Document ID | / |
Family ID | 20077187 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020772 |
Kind Code |
A1 |
Bas, Wlodzimierz ; et
al. |
February 5, 2004 |
Method and system for measuring active animal glue concentration in
industrial electrolytes
Abstract
A method consists in measuring ac impedance spectrum using gold,
platinum or carbon working ultramicroelectrodes (1). The direct
current DC potential pulse which overlaps with alternating current
AC signal of an amplitude in the range from 0.005 to 0.015 V and
frequency in the range from 10.sup.-2 to 10.sup.6, Hz is applied at
the electrode. The value of said DC potential pulse for a process
of copper electrorefining is in the range from -0.4 to -0.9 V in
relation to a platinum reference electrode (2). Resistance values
characteristic of a given electrolyte (E) are obtained from said AC
impedance spectrum and compared with standard characteristic
obtained by standard additions method. A measuring system consist
of electrodes (1, 2, 3) placed inside a measuring cell (4) filled
with flowing industrial electrolyte. The electrodes (1, 2, 3) are
joined to a spectrum analyser (12) controlled by a programming
apparatus (13)
Inventors: |
Bas, Wlodzimierz; (Glogow,
PL) ; Fuglewicz, Boguslaw; (Wroclaw, PL) ;
Garbaczewski, Jan; (Glogow, PL) ; Gladysz,
Olympia; (Wroclaw, PL) ; Jagiello, Jan;
(Glogow, PL) ; Los, Przemyalaw; (Wroclaw, PL)
; Malachowicz, Grzegorz; (Wroclaw, PL) ; Nosal,
Stanislaw; (Glogow, PL) ; Orzecki, Stanislaw;
(Glogow, PL) ; Plinska, Gtanislawa; (Oborniki
Slaskie, PL) ; Przysiezny, MIroslaw; (Glogow, PL)
; Romanowicz, Piotr; (Glogow, PL) ; Szwancyber,
Grzegorz; (Glogow, PL) ; Urbanowicz, Roman;
(Glogow, PL) ; Warmuz, Marian; (Glogow,
PL) |
Correspondence
Address: |
Horst M Kasper
13 Forest Drive
Warren
NJ
07059
US
|
Family ID: |
20077187 |
Appl. No.: |
10/344301 |
Filed: |
February 7, 2003 |
PCT Filed: |
April 2, 2001 |
PCT NO: |
PCT/PL01/00027 |
Current U.S.
Class: |
204/434 ;
205/574; 205/789 |
Current CPC
Class: |
G01N 27/026
20130101 |
Class at
Publication: |
204/434 ;
205/574; 205/789 |
International
Class: |
G01N 027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2000 |
PL |
P341922 |
Claims
1. A method of measuring active animal glue concentration in
industrial electrolytes, especially in copper electrorefining
process, using electrochemical impedance spectroscopy (EIS) in the
range of frequencies from 10.sup.-2 to 10.sup.6 Hz, characterized
by registering said AC impedance spectrum at an ultramicroelectrode
(gold, platinum or carbon) under said DC potentiostatic component
whose value is comprised in the range of electroreduction of metal
ions potential in industrial electrolyte, the most favourable value
for copper ions in the range from -0.4 to -0.9 V, in relation to a
platinum or copper reference electrode, and said potentiostatic
signal applied at the working electrode overlaps with said AC
signal of an amplitude in the range from 0.005 to 0.015 V, while
from the impedance spectrum obtained in this way the resistance
value characteristic of a given industrial electrolyte is
determined and said resistance value is compared with standard
resistance value determined experimentally for optimum animal glue
concentration on the basis of standard characteristic made by
standard additions method realised by impedance spectrum
registering.
2. The method defined in claim 1, wherein the resistance value
(R.sub.G) characteristic of a given electrolyte is obtained from
the point of intersection of impedance spectrum (W) on a complex
plane Z", Z' with real axis Z' at the side of low frequencies.
3. The method defined in claim 1, wherein the resistance value
characteristic of a given electrolyte (E) is obtained by an
approximation of a spectrum part using equivalent electric circuit
consisting of determined resistance (R.sub.CT) and capacitance (C)
connected in parallel which are in turn connected in series with
the second resistance (R.sub.S) defining high-frequency resistance
of an electrolyte (E).
4. The method defined in claim 1, wherein the resistance value
(R.sub.F) characteristic of a given electrolyte (E) is determined
as a real part of impedance measurement at one chosen frequency in
the range from 10 to 500 Hz.
5. A system for measuring active animal glue concentration in
industrial electrolytes, especially in copper electrorefining
process and said system comprises at least two measuring electrodes
placed inside a Faradaic cage characterized in that, that said
platinum, gold or carbon ultramicroelectrode (1) acting as said
working electrode has a diameter of 1-50 .mu.m, while said
reference electrode (2) has a surface of 0.1-0.6 cm.sup.2 and said
electrodes (1, 2, 3) are placed inside a measuring cell (4) which
is surrounded by an aqueous coat (5) and said measuring cell (4) is
connected to an electrolyte (E) tank (8) by an inlet pipe (7) and
an outlet pipe (9) is led out to an electrorefining system from
said measuring cell (4) said electrodes (1, 2, 3) are joined to
impedance spectrum analyser (12) whose controlling entry is joined
to said programming apparatus (13) exit while measuring exit is
joined to a registering entry of said programming apparatus
(13).
6. The system defined in claim 5, wherein said dosage programming
apparatus (13) exit is joined to a controlling entry of a glue
container (10).
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method and system for measuring
active animal glue concentration for use in particular in copper
electrorefining processes.
BACKGROUND OF THE INVENTION
[0002] Fire refined anode copper undergoes electrorefining in order
to obtain the highest quality copper. This process is carried out
in the following way: cast in the metallurgical process anodes are
hung in electrolytic tanks filled with electrolyte composed of
aqueous solution of copper sulphate and sulphuric acid.
[0003] Thin pure copper sheets acting as cathodes are placed
between the anodes. During copper electrolysis, copper is passing
from an anode into the solution while electrodeposition of copper
from the solution is taking place on a cathode.
[0004] The process of copper electrorefining is carried out at the
temperature of about 60.degree. C. and a continuous flow of
electrolyte through the electrolytic tanks is maintained. Copper is
deposited on the cathode in the form of crystals which tend to
assume irregular shapes, so called dendrites. The formation of
dendrites is highly inadvisable because sedimentation anode slime
tends to settle on them. Dendrites are also the main cause of
short-circuit which occurs between a cathode and an anode. Addition
of surface active substances such as thiourea and active animal
glue to the electrolyte prevents dendrites formation. These
additions are systematically used up during the process so their
quantity is replenished continuously. Cathodes of required quality
are obtained by using precisely defined quantities of additions.
Too small or too big doses of thiourea and active animal glue
always cause deterioration of cathode quality. Direct measurement
of active animal glue concentration in the electrolyte is not
possible since the mechanism of glue action to industrial
electrolyte has not been known so far. It is known, however, that
one of the significant elements of glue activity in the electrolyte
is inhibition of electron/charge transfer reaction due to copper
ion electrochemical reduction in the solution. The presence of glue
decreases electron/charge transfer rate thus the whole process of
cathodic reduction is controlled by rate of electron/charge
transfer process as well as adsorption on the electrode.
[0005] The method of defining surface-active substances such as
thiourea and animal glue content in copper electrorefining
composition is known from patent description SU 1742706 A1. On the
basis of copper electrode polarisation magnitude in copper
electrorefining solution at the current density in the range from
250 to 350 A/m.sup.2, the glue concentration is determined after
having eliminated thiourea by hydrogen peroxide. The thiourea
concentration is determined in accordance with earlier determined
glue content. The glue activated earlier in sulphate electrolyte at
the temperature of 60-65.degree. C. for 3-4 hours is used for
obtaining standard curves which enable to determine the components
concentrations.
[0006] This method has limited reproducibility because the shape of
polarisation curves depends on electrolyte composition in
particular on Cu (I) and Cu (II) concentration. Changes of these
ion concentrations may cause significant changes of potential
registered at the well-fitted current density. As a result,
accuracy of this method based on determining potential drop may
differ in some cases considerably from declared value of .+-.0.1
mg/l. Two determinations are performed in this method, thiourea is
removed in one sample so the determination time is long and the
whole process is relatively laborious. As there is always certain
concentration of animal glue and thiourea in industrial
electrolytes, said method implies performing all standard curves
for each sample, initial concentration value being virtually
unknown.
[0007] Electrochemical impedance spectroscopy is known from the
paper by Lo P. "AC Impedance Electrochemical Studies of Solid Rough
and Porous Electrodes, and Ultramicroelectrodes (UME)", School of
Medicine, Wroclaw 1996 as well as from the textbook by Bogusz W.,
Krok F.: Solid Electrolytes --Electrical Properties and Methods for
Measurement, WNT, Warsaw 1995. This method being an electrochemical
in situ method which may be used for electrochemical reaction
mechanism and kinetics studies at rough and porous electrodes. In
the case of these electrodes it is not possible to understand the
phenomena that occur at electrode/electrolyte interface without
understanding the electrode structure. The basic experimental
material of impedance spectroscopy is a set of sample impedance
values for chosen discrete frequencies covering the widest possible
range of about 10.sup.-3 Hz to radio frequency in the order of
several hundreds of kHz. The following measuring methods are used
in this range;
[0008] oscillographic methods for the highest frequencies,
[0009] bridges,
[0010] spectrum analysers FRA--Frequency Response Analysers,
[0011] time domain measurements combined with subsequent Fast
Fourierr Transformation (FFT).
[0012] In order to measure high impedances the studied system
should be placed inside a Faradaic cage.
[0013] The combination of impedance spectroscopy and
ultramicroelectrodes is particularly useful for studying
electrochemical cells, sensors and high impedance systems.
Ultramicroelectrodes are electrodes which have at least one linear
dimension in the order of several micrometers. They possess
numerous properties particularly useful for electrochemical
studies. As a result of their small dimensions both electrolyte
resistance R.sub.S (expressed in .OMEGA. cm.sup.2) and double layer
charging current are reduced to minimum.
OBJECTS OF INVENTION
[0014] I. The invention relates to a method of measuring active
animal glue concentration in industrial electrolytes, especially in
copper electrorefining, using electrochemical impedance
spectroscopy (EIS) in the range of frequencies 10.sup.-2-10.sup.6
Hz at an ultramicroelectrode.
[0015] The object of the invention is to register impedance
spectrum at a gold, platinum or carbon ultramicroelectrode under
conditions of DC potentiostatic signal the value of which is
comprised in the range of electroreduction metal ions potential in
industrial electrolyte, the most favourable value is for copper
ions from -0.4 to -0.9 V. Said registering occurs in relation to
platinum reference electrode and the DC potentiostatic signal
applied at the working ultramicroelectrode overlaps with AC signal
of an amplitude in the range from 0.005 to 0.015 V. Impedance
spectrum obtained in this way enables to determine the resistance
value characteristic of a given industrial electrolyte. Said
resistance value is compared to the standard resistance value
determined experimentally for optimum animal glue content on the
basis of standard characteristic made by standard additions method
obtained from impedance spectrum measurements.
[0016] The resistance value characteristic of a given electrolyte
is determined from the point of intersection of impedance spectrum
on a complex plane with real axis at the side of low frequencies or
by an approximation of a spectrum part using equivalent electric
circuit composed of determined resistance and capacity connected in
parallel which are in turn connected in series with the second
resistance defining high-frequency electrolyte resistance or as a
real part of impedance measurement at one chosen frequency in the
range from 10 to 500 Hz.
[0017] II. The invention relates to a system for measuring active
animal glue concentration in industrial electrolytes especially in
copper electrorefining process. Said system comprises at least two
electrodes: working and reference one. They are placed inside a
Faradaic cage.
[0018] The object of the invention is to use platinum, gold or
carbon ultramicroelectrode as a working electrode which has a
diameter of 1 to 50 .mu.m while a platinum or copper reference
electrode has a surface of 0.1-0.6 cm.sup.2. Both electrodes are
placed inside a measuring cell surrounded by an aqueous coat The
measuring cell is connected to an electrolyte tank by an inlet
pipe. An outlet pipe is led out from the measuring cell to
electrorefining system. The electrodes are connected to the
impedance spectrum analyser whose controlling entry is joined to a
programming apparatus exit while measuring exit is connected to a
recording entry of the programming apparatus. It is advisable that
dosage programming apparatus exit is joined to a controlling entry
of a glue container.
[0019] The studies of electrochemical methods have shown that
electrochemical impedance spectroscopy (EIS) being a method in situ
is the most suitable of all to study effectively animal glue in an
electrolyte. Combining electrochemical impedance spectroscopy (EIS)
with an ultramicroelectrode (UME) enables to shorten the
concentration measuring time to about two minutes (including
analysis of the results and cleaning of the working electrode). The
mass transport rate at an UME is significantly bigger than at a
normal size electrode which results in immediate establishing of
glue adsorption equilibrium (steady-state) at an UME. The
registered impedance spectrum can be used for determining active
animal glue concentration in a simple way because at low
frequencies steady-state is established at UME. This method, called
GlueDet, is in accordance with the invention. It is of about 3.5%
accuracy and high sensitivity of about 0.06 mg/l of active glue. By
sensitivity is meant the smallest value of entry signal change,
i.e. active animal glue concentration change causing measurable
exit signal change. In addition, the measurement of impedance
spectrum in the range of frequencies from several thousand Hz to
several Hz makes it possible to obtain such Faradaic parameters
during one experiment as for example: diffusion coefficient and
charge/electron transfer reaction rate constant. It is known that
glue presence in industrial electrolyte decreases the rate of
electron transfer process at electrode/electrolyte interface. It
should be expected then that charge transfer resistance should
increase when active animal glue concentration increases. The
combination of EIS and UME enable to obtain a very effective
measuring instrument of said kinetic effect.
[0020] The possibility of obtaining a steady-state at an UME at low
frequencies values permits to acquire a standard curve for the
dependence of the resistance measured in these conditions, i.e. in
an intersection point of impedance diagram on a complex plane with
real axis Z' at the side of low frequencies, on the glue
concentration. Said resistance is a sum of electrolyte and charge
transfer resistance the latter being a characteristic of charge
transfer kinetic process. Though the analysis of a whole spectrum
may provide significant information about kinetics and mechanism of
copper reduction process in industrial electrolytes, it can be said
that for analytical purposes the resistance analysis according to
glue concentration is sufficient. The method of glue determination
in accordance with the invention may also be used in kinetic
studies of glue hydrolysis in relation to time and temperature.
[0021] Standard curves measurements of resistance dependence upon
active glue concentration is carried out by the standard additions
method. This method is used because the matrix composition of
analysed sample is not known. The method proposed in the invention
is simple and does not require any additions or changes, e.g.
de-oxidation of analysed solution It has been assumed that said
method will be used for determining active glue concentration
because only part of the glue hydrolysis components show activity
in relation to copper electroprocessing. On the basis of the
literature data analysis it can be stated that active glue or
rather its hydrolysis products should possess adequately high molar
mass; it does not show activity below molar mass activity. It is
widely known that in order for the glue to show activity, its
hydrolysis products have to contain components whose molar mass is
higher than 10000. Higher glue components activity of greater molar
mass is explained by the possession of greater number of functional
groups which may adsorb strongly on the cathode surface.
[0022] Said measurement system and results analysis method are
simple and may be totally automated. It means that continuous
active glue concentration measurements may be carried out in
several measurement cycles automatically. The result of the
measurement is received on the monitor screen or printed directly
in mg/l of active animal glue in industrial electrolyte. The number
of studied cycle, a date and hour of carried determination may also
be given. Said system is totally automated and enables to control
active glue concentration in real time thus the active animal glue
dosage to industrial electrolyte may also be automated. The
operation time of one analysis is very short and does not exceed
two minutes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The object of the invention is shown by way of examples of
embodiment with reference to the accompanying drawings, in
which:
[0024] FIG. 1 is a diagram illustrating a system for measuring
animal glue concentration in industrial copper electrorefining.
[0025] FIG. 2 is an impedance spectrum on a complex plane, on
Y-axis imaginary part--Z", on X-axis real part Z'.
[0026] FIG. 3 is an equivalent circuit used for approximation of
the experimental results obtained at an UME.
[0027] FIG. 4 is a standard characteristic of resistance dependence
in relation to animal glue concentration in electrolyte.
EXAMPLES
Example 1
[0028] The described system is used for measuring animal glue
concentration in copper electrorefining system. Three electrodes,
working ultramicroelectrode (1) is made of gold wire of a diameter
40 .mu.m, auxiliary electrode (2) is a platinum plate 0.05 cm thick
and surface of 0.5 cm.sup.2, and calomel reference electrode (3)
are immersed up to 1 cm in the electrolyte inside a glass measuring
cell (4) surrounded by an aqueous coat (5). The system is placed in
a Faradaic cage (6). A pipe (7) whose inlet is put in a tank (8) of
a electrolyte (E) is inserted to the glass cell (4). The second
pipe (9) fastened in the glass cell is led out to electrorefining
system. An animal glue container (10) is connected by a pipe (11)
to the tank (8). The electrodes (1, 2, 3) are connected to an
electrochemical meter (12), i.e. spectrum analyser (FRA). The
controlling entry of the meter (12) is connected to an exit of a
programming apparatus (13) which comprises microcomputer Pentium
and a measuring exit is joined to a recording entry of the
programming apparatus (13). The dosage programming apparatus
exit/outlet (13) is connected to a controlling entry/inlet of glue
container (10).
Example 2
[0029] The method of determining standard characteristic is
described in the presented system. For given conditions of animal
glue dosage in industrial electrolyte (E) during copper
electrorefining process, standard resistance (R.sub.G)
characteristic is taken off in relation to active animal glue
concentration in the electrolyte using impedance spectroscopy
method for measuring several points which correspond to gradual
addition of defined glue portions. The results are approximated by
a linear relationship of said standard resistance vs. said active
animal concentration.
Example 3
[0030] The measurement of glue concentration in electrolyte (E) in
industrial process is carried out when there is a continuous flow
of electrolyte (E) through a measuring cell (4) at flow intensity
chosen appropriately for existing conditions. DC potentiostatic
signal of -0.5 V with superimposed AC signal of an amplitude of
0.010 V and frequency range from 200 kHz to 0.1 Hz is applied
cyclically by a programming apparatus (13). On the basis of the
registered spectrum, resistance value characteristic of the studied
electrolyte is determined. The determined value is written in a
standard characteristic from which can be read off animal glue
concentration. There are three methods to determine the resistance
characteristic of said electrolyte (E).
Example 4
[0031] The value of resistance (R.sub.G) characteristic of said
electrolyte (E) is read off from impedance spectrum (W) at the
point of its intersection with a real axis Z' at the side of low
frequencies.
Example 5
[0032] The value of resistance (R.sub.CT) is read from said
impedance spectrum W using approximation to said real axis Z'.
Example 6
[0033] The value of resistance (R.sub.F) is read off for a
frequency of 50 Hz using one point impedance measurement in said
electrolyte (E).
LIST OF SYMBOLS
[0034] 1--UME--working ultramicroelectrode
[0035] 2--platinum auxiliary electrode
[0036] 3--calomel reference electrode
[0037] 4--measuring cell
[0038] 5--aqueous coat
[0039] 6--Faradaic cage
[0040] 7--electrolyte delivering pipe
[0041] 8--electrolyte tank
[0042] 9--draining pipe
[0043] 10--glue container
[0044] 11--pipe
[0045] 12--FRA--Frequency Response Analysers
[0046] 13--programming apparatus with microcomputer Pentium
[0047] E--electrolyte
[0048] EIS--Electrochemical impedance spectroscopy
[0049] FFT--Fast Fourierr Transformation
[0050] AC--alternating current
[0051] DC--direct current
[0052] C--capacitance
[0053] R.sub.F, R.sub.G --characteristic resistance
[0054] R.sub.S--electrolyte resistance
[0055] R.sub.CT--charge resistance
[0056] W--impedance spectrum
* * * * *